How far away are those bats? In theory one may think that some of
them drown into the increased noise level of the mic, but I wouldn't think =
so.
Klas.
At 06:16 2008-06-06, you wrote:
>Hi Rob,
>Thanks for suggestion, but from the recordings, bat activity at
>least seems highly sensitive
>to temperature (warmer night in a cold interval =3D> a lot more bat
>calls). This is also
>reasonable since insect availability (assessed by light traps) ramps
>up when it is warmer.
>The important issue Klas's observation raised is that low detection
>of bat acoustic activity
>at low temperatures might result in part from lowered microphone
>sensitivity and a
>resulting decrease in detection volume. So how much is biological
>response and how
>much is instrument effect?
>
>There are a couple of detailed papers from a few decades ago that
>measured attenuation
>with distance for acoustic signals over a wide frequency range at
>biologically relevant
>temperatures and humidities (though not very cold if I recall
>correctly). The results are
>surprisingly complicated in the ultrasound.
>
>Bill
> > >Hi Klas,
> > >The idea of response changes with low temperature seems entirely
> > >reasonable. Can you
> > >suggest from tests or speculate on what would happen to sensitivity
> > >and frequency
> > >response?
> >
> > Hi Bill--
> > As you are running long takes, perhaps you could extract and compare
> > some samples from bitter cold and warmer nights a few days apart with
> > the mics in the exact same spot. While you're at it, it would be
> > interesting to ponder potential air density differences! :-) Rob D.
> >
> >
> > --
> >
>
>
>
>
>------------------------------------
>
>"While a picture is worth a thousand words, a
>sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause
>Yahoo! Groups Links
>
>
>
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